The present invention relates to micro-wave devices using the propagation of magnetostatic waves in a ferrimagnetic medium. Starting with a substrate formed for example by a &lt;111&gt; biased gallium and gadolinium garnet (GGG), there can be grown by epitaxy a thin ferrimagnetic layer of yttrium and iron garnet (YIG). This ferrimagnetic layer, whose thickness may vary between a few microns and a few tens of microns, is capable of propagating different types of magnetostatic waves with relatively small losses. Depending on the orientation of the polarizing magnetic field, surface or volume magnetostatic waves can be propagated. The speeds of propagation are substantially higher than those which are met with in surface acoustic wave devices, which facilitate the construction of devices operating at frequencies equal to or greater than gigahertz. Furthermore, the speed of propagation of the magnetostatic waves varies with the intensity of the polarizing magnetic field, which enables tunable devices to be obtained in the filter and resonator field. This interesting property also allows the characteristics of a dispersive or non-dispersive delay line to be adjusted.
In the field of surface acoustic wave devices, exchange structures are known formed from conducting strips insulated from each other. These structures are formed by photo-etching on the surface of a piezoelectric substrate. They act on the sharing of the ultrasonic energy to cause distribution, total transfer, concentration or reflection of this energy.
In the field of magnetostatic-wave devices, transducer structures, selective reflector gratings formed of insulated conducting strips and different absorption means are already known. However, with the use of exchange structures the field of application of magnetostatic waves can be substantially enlarged. Since the mode of manufacture of such exchange means may be the same as that of transducers and reflecting gratings, the configurations which comprise them can be easily achieved by photo-etching a metal film deposited or simply applied to one of the faces of the thin ferrimagnetic wafer along which the magnetostatic waves are propagated.